#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int F(int ret) {
	int f[100] = { 0,1,1 };
	for (int k = 2; k <= ret; k++)
		f[k] = f[k - 1] + f[k - 2];
	return f[ret];
}

int main() {
	int i;
	scanf("%d", &i);
	int M = F(i);
	printf("%d", M);
	return 0;
}